This invention is directed to a device for dampening the vibration and noise produced in a hydraulic installation.
Hydraulic appliances, particularly mixer valves for hot and cold water, under certain conditions of operation produce a vibration which is mainly due to cavitation phenomena and to the sharp deflections imposed on the flow path of water in the valve. This vibration is transmitted by the water to the supply tubes and to the main pipes. The vibration causes noise. This vibration is detrimental and the noise it produces is annoying. Furthermore, the amount of noise that can be produced is often regulated by law.
If no special means are provided to reduce the vibration the transmission of this vibration takes place without any noticeable damping due to the incompressibility of the water. The means usually adopted for limiting or reducing noise consist in compensating for the incompressibility of water by including, along the flow path of the water, elastically yielding regions formed by air pockets enclosed in envelopes of a flexible, usually elastomeric, material. For example, Italian Patent No. 1,141,569 discloses air pockets defined by annular envelopes having a C-shaped cross section inserted in the passages between the intakes of the tap body and the fixed plate controlling the water volume through which the water flows. According to German Patent No. 3,000,990 air pockets are defined by finned tubular envelopes inserted in the passages through which water flows between the intakes of the tap body and a fixed plate controlling the water volume. Furthermore, according to the German Patent No. 2,421,372 air pockets are defined by tubular envelopes located within passages provided for the water inlet in the body of a tap. Other arrangements are also known and they may be disposed either in a tap body or in the S-shaped connections usually employed for connecting a tap to water intakes. It is a feature common to all these arrangements that the envelopes enclosing the air pockets are located in the flow path of water so that the envelopes are in direct contact with the water flow. It was thought, until now, that direct contact between such envelopes and the water flow was essential to dampen vibration.
In these known and conventional devices the dampening action is due to the elastic resilience of the air enclosed in the pockets, which air is separated from the water by the envelopes of elastomeric material defining the air pockets. The presence of the envelopes reduces or limits the damping action of the air pockets; however, the envelopes are essential in order to keep the air in the pockets. Therefore, in order to improve the dampening action by reducing the hindrance of the envelopes, it is necessary for the envelopes to have a great deformability, namely, they should be thin. However, if an envelope is very thin the water flow contacting the thin envelope produces dynamic actions inducing a vibration in the envelope. This vibration is harmful and results in deterioration of the envelope. For this reason it is not possible to reduce the thickness and, therefore, the stiffness of the envelopes below certain limits. This inability to sufficiently reduce the thickness and stiffness of the envelopes greatly limits the effectiveness of known dampening means. Moreover, in certain cases the insertion of a tubular envelope in the flow path of the water is very difficult due to the limited space available. This is the case, for example, in those taps which are supplied through stiff tubes or hoses. To insert a dampening envelope in such taps would necessitate a noticeable and costly increase in the length of the tap body.
An object of this invention is to optimize the use of air pockets defined by envelopes of flexible material in order to dampen the vibration and noise in a hydraulic installation. Another object of the invention is to obtain a dampening action more effective than that which can be attained with conventional and known damping means. Another object is to allow the installation of an envelope defining an air pocket in locations with limited available space. Still another object of the invention is to provide arrangements of envelopes defining the air pockets in which the envelopes do not vibrate and do not deteriorate due to the water flow.